Ratchet wrench



Nov. 11, 1947. w. E. PUGH RATcHE'r WRENCH Filed Feb. 26, 1944 Q a/f'er.5 1 1 02 aim Patented Nov. 11, 1947 RATCHET WRENCH Walter E. Pugh,Sabina, Ohio, assignor to Honore G. Hubbard, Rockford, Ill.

Application February 26, 1944, Serial No. 523.962

9 Claims.

This invention relates to so-called ratchet wrenches and the generalobject is to provide such a wrench which is substantially more rugged inconstruction and durable in service operation than prior wrenches.

Another object is to provide for coaction of the pawl and ratchet teethin a novel manner such as to insure full engagement under allconditions.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which Figure 1 is an elevational View of aratchet wrench embodying thepresent invention.

Fig. 2 is a section taken along the line 2-2 of Fig. 1.

Figs. 3 and 4 are fragmentary sections taken alon the line 3-3 of Fig, 2with the parts conditioned for operation of the wrench in oppositedirections.

Figs. 5 and 6 are fragmentary views of parts of Fig. 3 showing the teethpartially and fully engaged on an enlarged scale.

While the invention is susceptible of various modifications andalternative constructions, I have shown in the drawings and will hereindescribe in detail the preferred embodiment. It is to be understood,however, that I do not intend to limit the invention by such disclosurebut aim to cover all modifications and alternative construe tionsfalling within the spirit and scope of the invention as expressed in theappended claims.

The improved wrench is of the same general shape as standard ratchetwrenches having a handle 5 forged integral with a hollow head 6containing the pawl and ratchet mechanism and covered by a removableplate I secured to the head by a screw 1. Herein a ratchet wheel 8having fine V-shaped teeth 9 is disposed between the plate 1 and thebottom ll] of a circular recess II in the head and preferably is formedintegral with a stud I2 journaled in the plate '7 and the head 6. Theprojecting end I3 of the stud is squared for reception in the usualsocket fittings which are held on the wrench by ball detent Hi. In thepresent instance, the ratchet teeth 9 are V-shaped having includedangles of 82 degrees and. intervening notches of 90 degrees.

The toothed periphery of the wheel 8 coacts with one of two pawls I5 andit which may be rendered active selectively to determine the directionof turning in which the wrench will be effective. These pawls comprisebars of generally square cross-section slidable endwise in slots IIwhich diverge along opposite edges of the wrench head 6 and extendgenerally tangentially of the wheel recess I I- into which the slotsopen. In this way, each pawl is held very rigidly against lateraldisplacement by the side walls 18 and IQ of the slots which walls areintegral with the Wrench head. Also, the wall l8 lies outwardly from theperiphery of the ratchet wheel and coacts with the toothed surface ofthe latter to form a tapered recess into which the toothed end of thepawl becomes wedged during each active stroke of the wrench handle. 7

Intermediate its ends, each pawl is formed with a cross-slot '20 whichis adapted to receive one pointed end of a cam bar 2| slidabletransversely of the wrench head in a slot 22 which communicates atopposite ends with the pawl slots H. A pin 23 rigid with the bar 2|projects through a slot 24 in the cover plate I and carries a button 25by which the bar may be shifted back and forth between the positionsshown in Figs. 3 and 4 to condition the wrench for turning of a nut orscrew in opposite directions.

Each pawl is urged toward the ratchet wheel by a light compressionspring 26 seated in the rear end of the pawl and acting against theclosed end of the slot II. The other or active end of the pawl extendsdiagonally of the slot H to conform approximately to the contour of theratchet wheel and is formed with a plurality of fine teeth 21, four inthe present instance, adapted to interfit with the ratchet teeth 9thereby providing a substantial surface area of engage-- ment betweenthe pawl and ratchet. For this purpose, the teeth 21 include angles ofdegrees complementing the angles of the ratchet notches, If the button25 is shifted from the full line position shown in Fig. 1, an inclinedcam surface 28 on the bar 2| will engage the corner 29 of the pawl l6and cam the latter backwardly out of engagement with the ratchet wheel.At the same time, the other end of the bar will be withdrawn from theslot 20 in the pawl l5 permitting the latter to be urged forwardly byits spring and thus brought into active engagement with the wheel 8(Fig. 3).

As shown in Figs. 1 and 3, the wrench is conditioned for clockwiseturning of a nut or screw. During such turning, the force of engagementbetween the pawl l5 and ratchet teeth is directed transversely of thepawl and outwardly toward the wall l8 which provides an extremely rigidbacking sustaining this force and extending along the pawl I5 to a pointimmediately adjacent the 3 wheel periphery. Since the active pawl isalso supported on the opposite side by the slot wall Hi, there is nopossibility of bending or tipping of the pawl or retraction of thelatter such as to permit slippage between the engaged teeth.

Now, when the handle is turned reversely, that is, counterclockwise, thefrictional resistance of the engaged nut or screw holds the ratchetwheel against turning with the handle and the pawl. As a result, theratchet teeth act as cams on the pawl teeth and shift the pawlbackwardly. The pawl teeth thus slip past the ratchet teeth and a newset of ratchet teeth is engaged by the pawl thereby again conditioningthe wrench for clockwise turning of a nut.

To condition the wrench for operation in the opposite orcounterclockwise direction, the button 25 is shifted from the dottedposition back to the full line position shown in Fig. 1 so as to movethe bar 2! into the slot 20 of the pawl l as shown in Fig. 4. In thismovement, a cam surface 30 engages the pawl surface 3i and retracts thepawl while the other end of the bar is withdrawn from the slot 20 in thepawl [6 allowing the latter to move into active position. This pawl thenacts in the manner above described to advance the wheel 8 in eachcounterclockwise motion of the handle.

Wrenches of the above character are used primarily to speed up thetightening of screws and nuts. Their operation is dependent on theexistence of suflicient friction on the thread of the nut or screw toovercome the force of the pawl spring 26 and permit slippage of theactive pawl past the ratchet teeth during retraction of the handle.Therefore, it is desirable to minimize the force exerted by the springs26. On the other hand, it is desirable, in order to minimize wear on andavoid breakage of the pawl and ratchet teeth, that the teeth always bebrought into full engagement before the full turning force becomeseffective, and this, in spite of rapid oscillation of the handle as iscustomary in the service use of a tool of this character. In otherwords, partial engagement of one ratchet and pawl tooth as shown in Fig.5 is to be avoided so that the full turning moment will not have to besustained by such a small tooth area.

The present invention meets the foregoing requirements by a novelconstruction and arrangement of the pawl and ratchet teeth by which, theactive pawl, if it does engage initially on the tip of only one ratchettooth as shown in Fig. 5, will be drawn automatically and independentlyof the spring force, into full engagement with the ratchet teeth asshown in Fig. 6 before the full turning force becomes effective. To thisend, the pawl teeth 2'! are extended around the ratchet wheel toward thesurface l8 far enough to insure in all degrees of engagement of theactive pawl, the creation of a force component directed parallel to thesurface l8 and of sufiicient magnitude to overcome, with a safe margin,the friction between the pawl and this surface.

Such a force component may be derived independently of the spring 26 andfrom the turning moment applied to the wrench handle, by constructingthe pawl and ratchet teeth and arranging the latter so that the angle abetween the handle surface i8 and the face 9* of the ratchet tooth firstengaged by the pawl will be greater than a locking angle at the initialposition of engagement with the pawl as shown in Fig. 5. This lockingangle varies with the materials of which the coacting surfaces arecomposed, with the degree of lubrication, and with the smoothness of thesurfaces. For smooth lubricated steel surfaces, it is ordinarilyconsidered as about 13 degrees. In the present instance, the angle isabout 19 degrees thereby allowing an ample margin of safety for thevarious surface conditions which may be encountered in service use.

With such a large angle, the reactionary force :12, which is directedperpendicular to the surface 9 when the handle is turned, produces acomponent 1 which is directed parallel to the surface l8 and toward theratchet and is of substantially greater magnitude than the opposingfriction forces acting on the pawl. As a result of this force 1 added tothe force of the spring 26, the pawl is drawn forward positively intofull contact with the ratchet as shown in Fig. 6 thereby insuring fullcontact of all of the pawl teeth before the full turning moment isapplied even though the handle motion is so rapid that only the firstpawl tooth engages the ratchet initially as shown in Fig. 5.

To ascertain the minimum value which the angle a must have in order toinsure the positive drawing in of the pawl (the force of the spring 25being neglected) it will first be observed that the outer side of theactive pawl and the side of the first pawl tooth to engage the ratchet(see Fig. 5) constitutes a wedge whose effective angle is 11. Accordingto the law of wedges, it can be shown that the locking angle a or theangle at which there is no motion of the wedge in either direction isthe angle whose tangent is where u is the coefficient of friction on thetwo sides of the wedge. For dry steel surfaces, the angle a isapproximately seventeen degrees, being somewhat lower, that isapproximately thirteen degrees as referred to above for lubricated steelsurfaces.

Comparing Figs. 5 and 6, it will be apparent that as the wedge moves infrom the Fig. 5 position, the angle a becomes progressively larger andreaches a value of about twenty-five degrees. the component y thusincreases correspondingly but this increase is offset to some extent bythe fact that the wedge angles a for the succeeding tooth areprogressively smaller. However, the resultant force paralleling thesurface I8 is always sufficient to overcome the friction forces opposingthe wedge movement and under all conditions insure that the pawl will bedrawn into full engagement with the ratchet even though the forceexerted by the spring 26 is comparatively small.

The novel coaction above described between the pawl and ratchet insureseven distribution of the turning movement over the full areas of allfour of the interchanging teeth. As a result, the possibility of toothbreakage or excessive wearing off of the first pawl tooth is avoided.The construction will, therefore, withstand the most severe service use.Moreover, the strength of the springs 26 may be reduced to a minimumthereby greatly increasing the usefulness of the wrench.

I claim as my invention:

1. A ratchet wrench having, in combination, a handle with a hollow headthereon, a shaft journaled in said head with one end projectingtherefrom, a ratchet wheel rigid with said shaft within said head andhaving V-shaped teeth around its periphery with the adjacent sides ofadjacent teethintersecting each other, a guide slot formed in said headand extending generally longitudinally of said handle and tangentiallyof said wheel into communication with said wheel recess, said slotdiverging from the longitudinal axis of said handle toward said wheelwith its outer side wall disposed outwardly beyond a tangent to thewheel periphery, a pawl slidable in said slot and having a plurality ofteeth complementing said ratchet teeth and arranged in a row extendingdiagonally of the pawl for full meshing engagement with the ratchetteeth, and a spring urging said pawl along said slot toward said wheel,said ratchet and pawl teeth being constructed and arranged so that theangle included between said outer side wall and the surface of theratchet tooth in the position of initial engagement with the first toothof the pawl is more. than a locking angle, the surfaces of said pawlteeth being inclined so as to come into full surface contact with themating ratchet tooth when the pawl and ratchet teeth are in full mesh.

2. A ratchet wrench having, in combination, an elongated handle with ahollow head thereon, a shaft journaled in said head with one endprojecting therefrom, a ratchet wheel rigid with said shaft within saidhead and having teeth around its periphery, a guide slot formed in saidhead and extending generally longitudinally of said handle andtangentially of said Wheel with its outer side wall disposed outwardlybeyond a tangent to the wheel periphery, a pawl slidable in said slot,spring means urging said pawl toward said wheel, and teeth on theforward end of said pawl engageable with said ratchet teeth and coactingtherewith in all degrees of engagement between the ratchet and pawlteeth to derive from the torque applied to said handle a force componentdirected along the pawl toward said wheel and having sufficientmagnitude to overcome the friction between said side wall and the pawland draw the pawl into full mesh with the ratchet teeth.

3. A ratchet wrench having, in combination, a handle with a headthereon, a ratchet wheel journaled in said head and having teeth aroundits periphery, a guide slot formed in said head and extending generallytangentially of said wheel into communication with said wheel recess, apawl slidable in said slot, spring means urging said pawl toward saidwheel, and teeth on the forward end of said pawl engageable successivelywith the teeth of said ratchet wheel as the pawl moves into full meshtherewith, the outer surface of said pawl and the oppositely facing sideof the first pawl tooth diverging toward said ratchet wheel andconstituting a wedge having an effective included angle which increasesprogressively from the initial to full engagement with a ratchet toothand in all degrees of such engagement is greater than a locking angle.

4. A ratchet wrench having, in combination, an elongated handle with ahead thereon, a ratchet wheel journaled in said head and having teetharound its periphery, a guide slot formed in said head and extendinglongitudinally of said handle and generally tangentially of said wheelinto communication with said wheel recess, a pawl slidable in said slot,spring means urging said pawl toward said wheel, and a tooth on theforward end of said pawl engageable with a tooth of said ratchet wheeland forming with the opposite side of the pawl a wedge diverging toward5. A ratchet wrench having, in combination,

a. handle with a hollow head thereon, a ratchet wheel journaled in saidhead and having teeth around its periphery, said head having a guideslot extending generally tangentially of said wheel and diverging fromthe longitudinal axis of said handle toward said wheel, a pawl slidable.in said slot, spring means urging said pawl toward said. wheel, and atooth on the forward end of said pawl engageable with one side of atooth on said ratchet wheel, the outer surface of said pawl and theengaged side of the ratchet tooth converging away from the wheel at anincluded angle which is greater than the angle at which the pawl islocked frictionally in engagement with the ratchet tooth and the surfaceof each pawl tooth being. inclined to come substantially into fullsurface contact with the corresponding ratchet tooth when the teeth arein full mesh.

6. A ratchet wrench having, in combination, an elongated handle with ahollow head thereon, a ratchet wheel journaled in said head and havingteeth around its periphery, said head having a guide slot extendinglongitudinally of the handle with its outer wall disposed generallytangentially of said wheel, a pawl slidable in said slot, means biasingsaid pawl toward said wheel, and a tooth on said pawl engageable withone side of a tooth on said wheel, said guide wall and the activesurfaces of said pawl and ratchet teeth being positioned to coact in allengaged positions thereof and derive from the torque applied to saidhandle a force component supplementing said biasing means sufficientlyto overcome the friction on said pawl and cause the latter to be movedinto full engagement with the ratchet teeth.

7. A ratchet wrench having, in combination, a handle with a hollow headthereon, a ratchet wheel journaled in said head and having teeth aroundits periphery, said head having a guide slot extending generallytangentially of said wheel and diverging from the longitudinal axis ofsaid handle toward said wheel, a pawl slidable in said slot, springmeans urging said pawl toward said wheel, and a tooth formed on theforward end of said pawl for full surface engagement of its outersurface with one side of a tooth on said ratchet wheel when the teethare in full mesh, the coacting surfaces of said pawl and ratchet beingangularly related so that the angle a included between the engagedratchet tooth surface and the outer surface of said guide slot at thepoint of initial engagement as shown in Fig. 5 is at least equal to thelocking angle for the materials of which the coacting surfaces of saidpawl, ratchet wheel, and head are composed.

8. A ratchet wrench having, in combination, a handle having a siderecess in one end portion thereof, a ratchet wheel journaled on saidhandle in said recess and having V-shaped teeth around its periphery, aguide slot formed in said handle and extending generally tangentially ofsaid wheel into communication with the wheel recess, a pawl slidable insaid slot, a first V- shaped tooth on said pawl having a surface whichis inclined relative to the mating ratchet tooth surface at the time ofinitial tip-to-tip engagement with the ratchet tooth, the inclina tionof the pawl and ratchet surfaces relative to each other decreasing asthe teeth are drawn into full mesh following said tip-to-tipengagement,- and other teeth on said pawl engageable with the ratchetteeth as the pawl is drawn into full mesh with the ratchet wheel, theouter surface of said pawl being inclined at greater than a lockingangle relative to the side of each ratchet tooth at the time of initialengagement with the tip of said first pawl tooth.

9. A ratchet wrench having, in combination, a handle having a siderecess, a ratchet wheel journaled in said recess and having V-shapedapproximately right angular teeth around its periphery, a guide slotformed in said handle and extending generally tangentially of said wheelinto communication with the wheel recess, a pawl slidable in said slot,and an approximately right angular V-shaped tooth on said pawl having asurface adapted for point contact with the mating ratchet tooth surfaceat the time of initial engagement followed by full surface contact asthe pawl tooth comes into full mesh with the ratchet tooth, theinclination of the pawl and ratchet surfaces at the time of such initialengagement being related to the inclination of said slot as to convertthe torque applied to said handle into a force component of sufiicientmagnitude and direction as to draw said pawl into full mesh with theratchet teeth.

WALTER E. PUGH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Lussier Jan. 5, 1886

